Think about Loose Coupling PerlMonks

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Hi Monks!

My question is about the following code example, taken as is from Wikipedia:

```@sorted = map  { \$_->[0] }
sort { \$a->[1] <=> \$b->[1] } # use numeric comparison
map  { [\$_, length(\$_)] }    # calculate the length of the s
+tring
@unsorted;

The above is pure Perl, not some generic pseudocode, and what worries me is that length() doesn't seem like a particularly good example for illustrating the concept. It has always been my understanding that in Perl, length(\$var) just returns whatever value is stored in the corresponding internal SV structure (Devel::Peek calls this field "CUR"; non-string/non-PV scalars don't have this attribute, more on them below). And if it is immediately available, why cache it?

What if we're "length()-sorting" an array of numeric scalars?

```#!/usr/bin/perl

use strict;
use Devel::Peek;

my @arr = (22, 5.555, 1, 4444, 333);

print Dump(\@arr, @arr+0), "\n\n\n";
# at this point, there are 4 IVs and one NV in our array;
# naturally, none of the elements have their length ("CUR") field set

my (\$retval, \$just_once);

my @sorted = sort {
# does this alter the internal structures of our actual
# array elements, turning IVs and NVs into PVIVs/PVNVs?
\$retval = length \$a <=> length \$b;

print Dump \@arr, @arr+0 if !\$just_once++;
# of course it does!

\$retval;
} @arr;

print "\nsorted = @sorted\n";

I might be missing something here, so please correct me if I'm wrong.

In reply to length() and the Schwartzian transform by hazylife

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